Interventions to enhance mental health and well-being within high risk industries such as the emergency services have typically focused on individual-level factors, though there is increasing interest in the role of organisational-level interventions. The aim of this study was to examine the importance of different aspects of manager support in determining the mental health of ambulance personnel. A cross-sectional survey was completed by ambulance personnel across two Australian states (N = 1,622). Demographics, manager support and mental health measures were assessed. Hierarchical multiple linear regressions were conducted to determine the explanatory influence of the employee's perception of the priority management places upon mental health issues (manager psychosocial safety climate) and managers' observed behaviours (manager behaviour) on employee common mental disorder and well-being within ambulance personnel. Of the 1,622 participants, 123 (7.6%) were found to be suffering from a likely mental disorder. Manager psychosocial safety climate accounted for a significant amount of the variance in levels of employee common mental health disorder symptoms (13%, p<0.01) and well-being (13%, p<0.01). Manager behaviour had a lesser, but still statistically significant influence upon symptoms of common mental disorder (7% of variance, p<0.01) and well-being (10% of variance, p<0.05). The perceived importance management places on mental health and managers' actual behaviour are related but distinct concepts, and each appears to impact employee mental health. While the overall variance explained by each factor was limited, the fact that each is potentially modifiable makes this finding important and highlights the significance of organisational and team-level interventions to promote employee well-being within emergency services and other high-risk occupations.